1. Field of the Invention
The present invention relates to heat exchangers, and more particularly, to a heat exchanger for use in an automotive air conditioning system.
2. Description of the Prior Art
Japanese Utility Model Application Publication No. 63-142586 discloses a heat exchanger, such as a condenser for use in an automotive air conditioning system. The condenser includes a plurality of adjacent, essentially flat tubes having an oval cross-section and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units are disposed between the adjacent flat tubes. The flat tubes and fin units jointly form a heat exchange region.
A pair of cylindrical header pipes are disposed perpendicular to the flat tubes and may have, for example, a clad construction. The diameter and length of the header pipes are substantially equal to the thickness and height of the heat exchange region, respectively. Accordingly, the header pipes protrude only negligibly relative to the heat exchange region when the condenser is assembled.
An inlet pipe, which is provided with a union joint at one end, is fixedly and hermetically connected to an upper portion of one of the header pipes. An outlet pipe, which is provided with a union joint at its one end, is fixedly and hermetically connected to a lower portion of the other header pipe. The inlet and outlet pipes protrude from opposite sides of the header pipes parallel to the width of the condenser. In this construction, the direction along which the width of the condenser extends is perpendicular to the direction of air flow which passes through the heat exchange region of the condenser. When the condenser is mounted in the restricted space of an automobile engine compartment, a reduction of the width of the heat exchange region of the condenser is required. A width reduction is required because of the outwardly extending inlet and outlet pipes. The reduction of the width of the heat exchange region decreases the area of the heat exchange region, thereby decreasing the heat exchanging capability of the condenser.
A similar defect appears in the condenser that is disclosed in Japanese Patent Application Publication No. 63-161394. In this condenser, the inlet and outlet pipes protrude from the ends of the header pipes along the longitudinal axes of the header pipes. Therefore, because of the longitudinally extending inlet and outlet pipes, the height of the heat exchange region of the condenser must be reduced when the condenser is mounted in an automobile engine compartment. The reduction in height of the heat exchange region decreases the area of the heat exchange region, which also decreases the heat exchanging capability of the condenser.
In order to avoid the above-mentioned defects, i.e. a reduction in either the height and/or width of the heat exchange region of the heat exchanger, one technique has been proposed. Referring to FIGS. 1 and 2 of the drawings, a heat exchanger, such as a condenser C for use in an automotive air conditioning system is illustrated. Condenser C includes a plurality of adjacent, essentially flat tubes 10 having oval cross-sections and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units 11 are disposed between adjacent flat tubes 10. Each flat tube 10 includes a vertical partition wall 101 which is integrally formed on an inner surface of each flat tube 10 along the longitudinal axis so as to divide the inner chamber of each flat tube 10 into two identical chamber sections. The plurality of corrugated fin units 11 and flat tubes 10 jointly form heat exchange region 100.
Cylindrical header pipes 12 (only one of them being shown in FIGS. 1 and 2) having opposite open ends are disposed perpendicular to flat tubes 10 and may be of a clad construction. The opposite open ends of the header pipes are fixedly and hermetically plugged by caps 121 (only one of them being shown in FIG. 1).
In the assembly process, the opposite ends of each flat tube 10 penetrate the header pipes and terminate at the center of the inner periphery of each header pipe. Therefore, each of the header pipes and the opposite ends of flat tubes 10 are fully supported and fixedly attached when assembled. Effective brazing of the tubes and header pipes can thus be successfully accomplished after the assembly of condenser C.
The header pipe diameter and length are substantially equal to the heat exchange region thickness and height, respectively. Accordingly, the header pipes protrude only negligibly relative to heat exchange region 100 when condenser C is assembled.
A plate 102 having a generally U-shaped cross-section is fixedly disposed on an upper end of heat exchange region 100, and is fixedly connected to an outer peripheral surface or the uppermost end of the header pipes by, for example, brazing. Though not illustrated in FIGS. 1 and 2, another plate identical to plate 102 is fixedly disposed on a lower end of heat exchange region 100, and is fixedly connected to the outer peripheral surface on the lowermost end of the header pipes by, for example, brazing. The structural strength of the condenser is reinforced by the use of the pair of plates.
Circular opening 122 has a diameter which is slightly greater than the outer diameter H' of an inlet pipe 13 which is described in further detail below. Circular opening 122 is formed at an upper portion of header pipe 12 where an upper pair of adjacent flat tubes 10 penetrate cylindrical header pipe 12. Outer diameter H' of inlet pipe 13 is designed to be of a length greater than the length of interval L, which is the distance between a pair of adjacent flat tubes 10 located at the upper portion of heat exchange region 100.
One end of cylindrical inlet pipe 13 is inserted into opening 122 and is connected thereto by, for example, brazing. The other end or free end of inlet pipe 13 is provided with a union joint (not shown). Though not illustrated in FIGS. 1 and 2, a cylindrical outlet pipe is provided with a union joint at the free end thereof and is connected to a lower portion of the other head pipe in the same manner as described above. The inlet and outlet pipes protrude from the header pipes on opposite sides of condenser C parallel to the thickness or depth of the condenser. In this construction, the thickness or depth dimension of the condenser is parallel with the direction of air flow passing therethrough, as indicated by arrow A. Accordingly, a reduction in the width and/or height of heat exchange region 100, to fit within an engine compartment, is not required, because of the positions of the inlet and outlet pipes. Therefore, the heat exchanging capability of condenser C is maintained.
The manner of connecting the outlet pipe to the other header pipe is identical to the manner of connecting inlet pipe 13 to header pipe 12. Therefore, hereinafter, the manner described for connecting inlet pipe 13 to header pipe 12 will be representative only. Thus, those features described for inlet pipe 13 can readily be applied to the outlet pipe.
As illustrated in FIG. 1, outer diameter H' of inlet pipe 13 is designed to be of a length greater than the length of interval L. Therefore, the end of inlet pipe 13 cannot be sufficiently inserted into opening 122 because of interference between it and the ends of the adjacent flat tubes 10 located at the upper portion of heat exchange region 100. The brazing process is conducted after the assembly of the condenser. When the end of inlet pipe 13 is not fully supported in opening 122, the end of inlet pipe 13 is defectively brazed to an inner peripheral surface of opening 122. Therefore, leakage of the refrigerant fluid from an interior of header pipe 12 to the atmosphere can occur.